Why Shouldn’t You Sleep With Light ‘ON’?

why shouldn’t you sleep with light ‘on

Sleep is an important part of daily routine. We spend nearly one-third of our life sleeping. Quality sleep in enough quantities and at the right time are as necessary for survival as food and water. In the absence of sleep, brain cannot form or maintain pathways that are essential for learning and creating new memories. Lack of sleep can make it difficult to concentrate and slows down responses.[1]

Now, a study, conducted at the Northwestern University, has made a startling discovery – sleeping with lights switched on can increase your risk of diabetes.[2]

The study, which was published in the journal, Sleep recruited 20 healthy adult volunteers in the age group of 18 to 40 years. They had to spend 2 nights and 3 days in the lab. On their first night, they were made to sleep in pitch black darkness. On the second night, half of them slept in the dark again, whereas the other half, slept in a room that had a bright overhead light switched on.

While the volunteers were sleeping, researchers tracked their vital signs, leg and eye movements, and brain wave activity. Hourly blood samples were taken to determine the amount of melatonin in the body. Melatonin is responsible for regulating the circadian rhythm in the body and its level typically rises when the body is asleep. In the morning, the researchers conducted a glucose tolerance tests on these volunteers, which showed astonishing results.


It was found that by merely sleeping under the bright light, the insulin resistance in the body increased, which is a major risk factor for diabetes. Insulin is a hormone secreted by the pancreas and helps the cells of the body to absorb glucose. In this way, insulin helps in maintaining the blood glucose levels in the body. Getting exposed to bright light for one night while sleeping acutely impacted the level of insulin resistance in the body.

Previous research had already linked poor sleep quality to increased risk of several diseases like breast cancer, depression and prostate cancer. Now, the recent studies have added metabolic disorders like diabetes to the list.

Sleep disturbances affect more than 25% of the general population and nearly 50% of the adults. Adults, who are at a risk of developing stroke, heart diseases and diabetes, need to improve the quality of their sleep in order to prevent and treat the epidemic of diabetes type II and obesity. This can also help in improving the quality of life of people suffering from sleep disturbances.

Although this study is in its preliminary stages yet, it is suggested that people should stay away from falling asleep on the couch in front of the television at night.